She's really in her element at parties.

她在社交聚会上真是如鱼得水。

《牛津词典》

My stepmother was in her element, organizing everything.

我继母那时如鱼得水，安排着所有一切。

《柯林斯英汉双解大词典》

She was in her element. When she sensed tension between us, she ran from one to the other to assure us that we were good and she loved us.

在感觉到我们之间的紧张气氛时，她就从一个人这儿跑到另一个人那里去，向我们表明，我们的关系是融洽的，她爱我们。

youdao

By the arrival of her third decade on the throne, she was in her element.

CNN: Elizabeth II: Young queen who grew into a modern monarch

Roode, who grew up on a nearby farm, is relaxed--completely in her element.

FORBES: Bush Baby

She's more about country living and was in her element watching an equine display by the Republican Guard in Paris.

CNN: Camilla, queen in waiting, makes Paris debut